Vaccine for goose bumps

dice-6Things happen according to their probabilities. Although trivial, we easily forget that. Some events are so amazing that we are truly tempted to think of them as signs of supernatural forces. I propose here a double-shot vaccine against this weakness of the mind.

I have a good friend, who is a Brazilian physicist married to an Austrian woman who speaks excellent Portuguese. Few years back, when we still lived in Vienna, this friend came to tell me that he had met another Brazilian physicist, graduate from his University, married to an Austrian who spoken perfect Portuguese. Not only that was true, but this person, now a new friend, came to live in the same floor of the same building that I lived there! Amazing coincidence, no?

But then, to put things in perspective, take this other case. A couple of years later, when I was living in Haarlem, my wife and I were invited for dinner with friends. There were other three couples there. Two of them were Brazilian engineers living in Haarlem, married to Dutch women who spoken perfect Portuguese.

Then, it seems that to meet a “Brazilian technical professionals living in Europe, married to European women who speak Portuguese” doesn’t sound so amazing anymore.

In fact, the degree of coincidence is arbitrarily defined. To have four couples in my list, I wrote “Brazilian technical professionals”. If I had written “Brazilian physicists”, then my list would contain only two couples.

This arbitrariness about how an event is understood and told is the true source of the coincidences.

In the dinner in Haarlem, one of the Dutch women told us (in Portuguese, naturally) how once she was travelling with friends in two cars in a motorway. At some point – she told – she felt an intense feeling of fear. Minutes later, her car was trapped in a traffic jam. The reason: the second car with her friends had been involved in a terrible accident.

She interpreted the event “to be afraid, then find her friends in an accident” as a sign of premonition.

To be afraid while you travel in high speed is not really a rare event. To be travelling with friends in two cars and one of them getting involved in an accident don’t sound so common, but certainly isn’t rare either. But to experience both events within minutes causes goose bumps; and people start to wonder about premonition, guardian angel, fate, and other supernatural explications.

Facing amazing events like this, there are two things we must always consider before bringing magic explanations to stage. It’s a double-shot vaccine against goose bumps.

  • First shot, we must always ask: In how many other ways the event could have happened and it would still cause goose bumps?

Suppose that instead of feeling afraid, she had had a dream about accidents in the previous night. She would probably still correlate the events. But she could have dreamt about accidents two nights before, or one week. (How many nights between the dream and accident would be needed to still feel the correlation?) Maybe, instead of her, other occupant of the car could have dreamt about accidents, and she would still be amazed.

What seems to be a rare event is usually a mind construction after the facts: we selectively put together only those elements that fulfill the feeling of rare. The repertoire of these elements is always immense. They can contain any routine facts (dreams, intuitions) happening to many people (any occupant of the car or a close relative), in a relatively undetermined time (from few minutes to several days before).

  • Second shot: we must always ask when facing the improbable: how common should be that event given the total population size?

Consider all hundred million trips in motorways that are done every year. The number of those trips with friends in two cars should still be immense. And even the number of double-car trips with one of them involved in an accident should still be quite large.

Then, what is uncommon from the personal perspective is just common from the population perspective.

I leave for you a challenge: take your own amazing coincidence. Then, apply these two tests to it. If after that, it still looks rare, congratulations, you may be facing a supernatural event.

It might sound useless exercise, but to inoculate ourselves against cognitive illusions is crazily important. You know, the problem with people who don’t understand probabilities is that they are surrounded by governments and companies that understand them pretty well.


  • Once I met a girl in a Calcutta-Dubai flight who turned out to be a neighbor living few blocks from me in Mülheim. Amazing, no? And about you? Share your amazing coincidence here. I don’t believe in witches, but I love them.
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  • After the vaccine against goose bumps, you may need glasses for gut feelings.

Categories: Cognitive Sciences, Philosophy of Science, Science, Scientific Culture

Tags: , , , , ,

3 replies

  1. A lot of Coincidences happening with me, but my favorite one is when I am thinking about something and in the next day I find someone on twitter, facebook or youtube talking about the same thing. And it is really amazing if there is a question or something I am wondering about it and in the next day I get the answer without searching.

    • I know the feeliing. I also like it. That’s the Zeitgeist. Everytime I have a new idea in my research projects, I run to get it implemented as fast as I can. I know, other people will most certainly be thinking about the same things at the same time.


  1. It’s all your fault if the universe goes banana | Much Bigger Outside

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